PHYSIOLOGY, 99” 
shadow of the larger ones. Every gardener and 
forester knows this, and he can only hope for suc- 
cess in his art, by attending to this provision of na- 
tune *. 
§ 279, 
What vegetables imbibe from the atmosphere is 
not inconsiderable. All succulent plants grow in 
dry places, and in general the most succulent plants 
_ of the globe, are found in the most barren and arid 
spots. ‘The Karro fields of the Cape of Good Hope, - 
where it rains a few weeks only in winter, but is 
hot and dry during summer, are adorned with num- 
berless succulent plants, which can imbibe nothing 
from the ground, but are always full of juice, and 
grow weil. Can those plants receive their food from 
any other source but the atmosphere? We find even 
that they suffer in our gardens from moisture, and 
soon become rotten, whereas they grow well, when 
little or not at all supplied with water. 
Rain, besides the above mentioned use, to moisten 
the ground, furnishes plants with water for decom- 
position and keeps their pores open, and fit for the 
transpiration of gases. In very dry weather, we 
will find with a microscope most of the pores filled 
with dust. If the drought continues long, and the 
dust is accumulated, then the leaves fade away, be- 
cause they can no longer perform their offices. A 
species of maple, the Acer platanoides, suffers most 
* Opium is said to affect the irritability of plants materially, 
pay even to destroy it entirely. ; 
9 : and 
